Expression of p16, p53 and Ki-67 proteins in the progression of epithelial dysplasia of the oral cavity.

BACKGROUND

The overexpression of the protein products of genes associated with the cell cycle tumour protein53 (p53), cyclin-dependent kinase inhibitor 2A (p16) and antigen identified by monoclonal antibody Ki-67 (Ki-67) is apparently of great significance. This study evaluated the immunohistochemical expression of these proteins in precancerous lesions and in carcinoma of the oral cavity.

MATERIALS AND METHODS

The nuclear expression of p53 and Ki-67 and nuclear and/or cytoplasmic expression of p16 protein was examined in 54 biopsy specimens from the oral cavity obtained over a period of 3 years. The samples included 18 cases of normal/hyperplastic mucosa, 25 cases of dysplasia and 11 cases of invasive squamous cell carcinoma. The specimens were grouped into three categories: 1 = no or mild dysplasia, 2 = moderate or severe dysplasia, and 3 = invasive carcinoma.

RESULTS

p16 was negative in all the group 1 specimens, while both p53 and Ki-67, when present, were limited to the cells of the basal layer. In the group 2 specimens, the number of p16-, p53-, and Ki-67-positive cells increased as the grade of dysplasia progressed. In group 3 (invasive carcinomas), p53 and p16 expression occurred respectively in 81.8% and 54.5% of cases, while Ki-67 was elevated in all the cases.

CONCLUSION

The expression of the cell-cycle proteins p16 and p53 in the dysplastic epithelium, in association with Ki-67, may represent significant markers to recognize evolution of precancerous disease in the oral cavity and to improve identification of the degree of dysplasia.